I got one for christmas (Acer 720) and it's brilliant:
Light
Long battery life (7-8 hours)
Instant on or 7 second boot from cold (only done this once since xmas to for an OS update which installs completely in the background)
Plenty fast enough (plus it won't slow down over time)
16Gb SSD for downloads/files, etc
HDMI, usb and SD card slots
I can easily connect/use/control my work PC or the iMac at home using Chrome Remote Desktop.
Google apps are very good.

We have iPads and Android tablets in the house and I think the Chromebook is the best by miles if what you're doing involves any typing whatsoever.

They are amazing, frankly. They are limited in what they can do, but that allows them to be optimised for it. Hard to describe how fast it is! £200 and it's at least an order of magnitude faster than my work laptop which is a quad core i7 that cost 11 times as much! Ok so it does more, but that is a double edged sword - a lot of the junk my work PC had to load is anti malware and corporate spyware yo make sure I haven't installed anything bad.

Treat it as a secure internet surfing tool and it is fabulous. Totally hassle free and foolproof. Battery and speed same as the day we bought it. Cold start to surfing in about 15 seconds.

If you have other devices, then I'd 100% say get one - much faster and easier than kid's Samsung tablet, with no issues about anti-virus software etc.

But.....As a total laptop replacement it is pretty useless. Very slow with photos, very limited apps, half the google stuff cannot work on it, printing a faff, documents a faff, some pdfs don't work (e.g. couldn't fill in a downloaded bank form last week) problems with listing stuff on ebay etc etc.

Because it's not running anything other than a browser in effect. As such updates happen when the app or website you're using updates.

It is slightly disingenuous to say that it won't slow down though as what we do increasingly uses more performance so in reality, it will seem to get slower though less than a windows computer which is allowed down over time by patching, etc.

Cos it's optimised to run just one thing, Google Chrome. You can't install anything else on it, which is the reason why Windows can get slower with time. The OS is also a dedicated OS that doesn't allow you to do anything either hence is stripped down.

It's a cloud terminal, in reality. It's never going to replace Windows obviously, but it offers a real alternative to the concept of the PC. Modern PCs are phenomenally powerful, a complete waste just for looking at pictures of cats and insulting people.

It will slow down over time but only because google will update ChromeOS to add more features/capability and reflect current day hardware capability and software protocols/technologies. *But* that timespan will be a long one And I guess you have the option of not accepting new OS releases in the future if you're aware that one might be a performance step too far for your current hardware.

•Playing Games: Depending on how you play games on your computer, you may be in luck or this may be a big speed bump. If you play web-based games in your browser, Chrome OS allows you to play the same Flash and HTML-based games. The Chrome web store contains some popular games, such as Angry Birds and Cut the Rope. However, you can’t install Windows software (or any local software), so you can’t play PC games. They can be ported to the browser via native client — for example, you can play Bastion on a Chromebook — but few games have been.

Main reason for saying won't slow down is ssd. As no moving parts like a HDD that slow down as they get older/fuller

Not true. HDDs don't slow down over time, at least not until right before they fail. They do get fragmented - as you delete files and add new ones, files end up in smaller and smaller pieces all over the disk. However this is not such an issue these days, I think that Windows does some management of this as it goes along. This also happens to SSDs but it doens't make it slower, ebcause it can access any part of the disk in the same time - with an HDD, the head has to move around on the disk.

The real reason Windows slows down over time is because we keep installing more stuff. If you never installed anything, it wouldn't slow down, or would only slow down slightly. If you do format and re-install Windows on an old PC it becomes as quick as new again - try it if you don't believe me

can they run flash on websites etc?

As far as I can tell the Chrome browser is identical to the PC one (but faster!). So everything that works in Chrome should also work. Since I've been using Chrome for years on PC, it has the nice side-effect that all my bookmarks etc sync perfectly, and any apps I add on the Chromebook I can still use exactly the same on my PC!

You can get them with 3G build-in yes, as an option. Just need a SIM card from your preferred mobile operator. Probably more convenient than a mifi type thing really - the mifi needs to have its own battery charged etc.

Hmmm, thinking about it, it would probably be cheaper to pay for tethering on my existing 3 contract.

It's between one of these and an iPad mini (not a direct comparison, more of a budget comparison) - I want to be able to take something to work with me for online ordering from screwfix etc (phone does job but a proper browser is a bit more detailed) and inputting my daily business spends.

We're kinda apple dna'd here but I see no reason why one of these wouldn't fit in as a standalone. It's not a different OS, just chrome in a box, so to speak.

Hmmm, thinking about it, it would probably be cheaper to pay for tethering on my existing 3 contract.

I pay I dunno, £5 or something for 2GB of 4G data on my phone. I'll cancel my dongle SIM when I can I think. However, 2-3 hours of tethering use means my battery is dead by early evening, so it's not ideal. Orange gave me 1Gb for £5/mo which may be worth it for the convenience of one battery and being able to open the laptop and go.

As for comparing with a small tablet - we just got a hudl (Chromebook + 7" tablet was the same price as a Windows laptop!) for family use, and it's frankly difficult for surfing on. Typing is terribly inconvenient. Too big to type two-thumbed as on a phone, and on my lap it's just too much hunching over.

I'm a fast typist, so for me using the Chromebook is far better and quicker. Also, websites don't have to be 'optimised for touch' since it's standard mouse + keyboard.